CVE-2024-34476 is a vulnerability identified in Open5GS, an open-source 5G core network implementation, affecting versions before 2.7.1. The flaw is a reachable assertion failure located in the AMF (Access and Mobility Management Function) component, specifically within the ogs_nas_encrypt function in the lib/nas/common/security.c source file. The vulnerability arises due to improper handling of the pkbuf->len parameter when processing NAS (Non-Access Stratum) messages sent from a UE (User Equipment). An attacker can craft malicious NAS messages that trigger this assertion failure, causing the AMF process to crash. This crash leads to a denial of service condition, disrupting the availability of the AMF service, which is critical for managing mobility and session states in 5G networks. The CVSS v3.1 base score is 5.3, reflecting medium severity, with an attack vector of network (AV:N), low attack complexity (AC:L), no privileges required (PR:N), no user interaction (UI:N), and impact limited to availability (A:L) without affecting confidentiality or integrity. The vulnerability is classified under CWE-805 (buffer access with incorrect length value), indicating a logic or boundary check issue. No known exploits have been reported in the wild, and no official patches are linked yet, though upgrading to Open5GS 2.7.1 or later is recommended once available. This vulnerability highlights the importance of robust input validation and error handling in telecom protocol implementations to prevent service disruptions.

The primary impact of CVE-2024-34476 is a denial of service (DoS) condition caused by the crash of the AMF component in Open5GS. Since the AMF is a critical function in 5G core networks responsible for managing user mobility and session states, its unavailability can disrupt network services for subscribers. This can lead to dropped connections, failed handovers, and degraded user experience. Telecom operators relying on Open5GS for their 5G core infrastructure may face service outages or instability, potentially affecting large numbers of users. Although there is no direct impact on confidentiality or data integrity, the availability disruption can have cascading effects on dependent services and network reliability. The ease of exploitation is relatively high as no authentication or user interaction is required, and the attack vector is network-based, meaning remote attackers can trigger the crash by sending crafted NAS messages. The scope of affected systems is limited to deployments using vulnerable Open5GS versions, but given the growing adoption of Open5GS in private and public 5G networks, the potential reach is significant. No known exploits in the wild reduce immediate risk, but the vulnerability should be addressed promptly to avoid future exploitation.

Organizations using Open5GS should monitor for the release of version 2.7.1 or later, which addresses this vulnerability, and apply the update as soon as it becomes available. In the interim, network administrators can implement filtering rules to block or scrutinize suspicious NAS messages from untrusted or unknown UEs to reduce exposure. Deploying anomaly detection systems that monitor NAS message patterns may help identify attempts to exploit this vulnerability. Network segmentation and strict access controls on the 5G core network components can limit the attack surface. Additionally, conducting thorough testing of NAS message handling and implementing robust input validation and boundary checks in custom or forked Open5GS deployments can prevent similar issues. Maintaining up-to-date backups and having failover mechanisms for AMF services can reduce downtime impact in case of crashes. Collaboration with Open5GS community and vendors for timely patches and security advisories is also recommended.